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The WCAG Criteria resource provides complete reference data for all WCAG 2.1 success criteria, including conformance levels, POUR principles, affected user groups, and suggested remediation actions.

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URI Patterns

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wcag://criteria
static
Complete list of all WCAG 2.1 criteria (78 total)
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wcag://criteria/{id}
template
Specific criterion by ID (e.g., 1.4.3, 2.4.7)
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wcag://criteria/level/{level}
template
Filter criteria by conformance level
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wcag://criteria/principle/{principle}
template
Filter criteria by POUR principle

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POUR Principles

WCAG 2.1 organizes criteria under four principles:
PrincipleURIDescription
Perceivablewcag://criteria/principle/perceivableInformation must be presentable to users in ways they can perceive
Operablewcag://criteria/principle/operableUI components must be operable by all users
Understandablewcag://criteria/principle/understandableInformation and operation must be understandable
Robustwcag://criteria/principle/robustContent must work with current and future assistive technologies

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Response Schema

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Single Criterion

When requesting a specific criterion (e.g., wcag://criteria/1.4.3):
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id
string
required
WCAG criterion identifier (e.g., "1.4.3")
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title
string
required
Official criterion title (e.g., "Contrast (Minimum)")
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level
string
required
Conformance level: "A", "AA", or "AAA"
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principle
string
required
POUR principle: "perceivable", "operable", "understandable", or "robust"
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guideline
string
required
Parent guideline ID (e.g., "1.4" for Distinguishable)
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description
string
required
Brief explanation of the requirement
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affectedUsers
string[]
required
User groups impacted by violations (e.g., ["low-vision", "color-blind"])
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suggestedActions
string[]
required
Remediation recommendations

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Multiple Criteria

When requesting filtered lists (e.g., wcag://criteria/level/AA), the response is an array of criterion objects with the same schema.

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Examples

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Get a Specific Criterion

const result = await client.readResource({ 
  uri: 'wcag://criteria/1.4.3' 
});

const criterion = JSON.parse(result.contents[0].text);
Response: 
{
  "id": "1.4.3",
  "title": "Contrast (Minimum)",
  "level": "AA",
  "principle": "perceivable",
  "guideline": "1.4",
  "description": "The visual presentation of text has a contrast ratio of at least 4.5:1",
  "affectedUsers": ["low-vision", "color-blind"],
  "suggestedActions": ["Ensure text has sufficient contrast against background"]
}

​
Get All Level AA Criteria

const result = await client.readResource({ 
  uri: 'wcag://criteria/level/AA' 
});

const criteria = JSON.parse(result.contents[0].text);
console.log(`Found ${criteria.length} Level AA criteria`);
// Output: Found 20 Level AA criteria

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Get All Perceivable Criteria

const result = await client.readResource({ 
  uri: 'wcag://criteria/principle/perceivable' 
});

const criteria = JSON.parse(result.contents[0].text);
console.log(`Perceivable principle has ${criteria.length} criteria`);
Returns: All criteria under Guidelines 1.1 through 1.4 (Non-text Content, Time-based Media, Adaptable, Distinguishable)

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Get All Criteria

const result = await client.readResource({ 
  uri: 'wcag://criteria' 
});

const allCriteria = JSON.parse(result.contents[0].text);
console.log(`Total WCAG 2.1 criteria: ${allCriteria.length}`);
// Output: Total WCAG 2.1 criteria: 78

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Quick Reference Tables

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Level A (Must Have)

Fundamental accessibility features required for basic access:
IDTitleAffected UsersGuideline
1.1.1Non-text Contentscreen-reader, low-visionText Alternatives
1.3.1Info and Relationshipsscreen-readerAdaptable
2.1.1Keyboardmotor-impairment, keyboard-onlyKeyboard Accessible
2.4.1Bypass Blocksscreen-reader, keyboard-onlyNavigable
4.1.2Name, Role, Valuescreen-readerCompatible

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Level AA (Should Have)

Additional features addressing common barriers:
IDTitleAffected UsersGuideline
1.4.3Contrast (Minimum)low-vision, color-blindDistinguishable
1.4.4Resize Textlow-visionDistinguishable
2.4.6Headings and Labelsscreen-reader, cognitiveNavigable
2.4.7Focus Visiblekeyboard-onlyNavigable
3.2.4Consistent IdentificationcognitivePredictable

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Level AAA (Nice to Have)

Enhanced features for optimal accessibility:
IDTitleAffected UsersGuideline
1.4.6Contrast (Enhanced)low-visionDistinguishable
2.4.9Link Purpose (Link Only)screen-readerNavigable
3.1.5Reading LevelcognitiveReadable
2.5.5Target Sizemotor-impairmentInput Modalities

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Common Use Cases

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Look Up Issue Context

When an analysis tool reports a WCAG violation: 
// Analysis returns: { wcagCriterion: "1.4.3", ... }
const violation = analysisResult.violations[0];

const criterion = await client.readResource({ 
  uri: `wcag://criteria/${violation.wcagCriterion}` 
});

const data = JSON.parse(criterion.contents[0].text);

console.log(`Issue: ${data.title}`);
console.log(`Affected users: ${data.affectedUsers.join(', ')}`);
console.log(`How to fix: ${data.suggestedActions[0]}`);

​
Build Compliance Checklist

Generate a checklist for a specific conformance level: 
const result = await client.readResource({ 
  uri: 'wcag://criteria/level/AA' 
});

const criteria = JSON.parse(result.contents[0].text);

criteria.forEach(c => {
  console.log(`[ ] ${c.id}: ${c.title}`);
});

​
Prioritize Remediation

Find all criteria affecting a specific user group: 
const result = await client.readResource({ 
  uri: 'wcag://criteria' 
});

const allCriteria = JSON.parse(result.contents[0].text);

const screenReaderIssues = allCriteria.filter(c => 
  c.affectedUsers.includes('screen-reader')
);

console.log(`${screenReaderIssues.length} criteria affect screen reader users`);

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Filter by Principle

Focus remediation on one POUR principle at a time: 
const result = await client.readResource({ 
  uri: 'wcag://criteria/principle/operable' 
});

const operableCriteria = JSON.parse(result.contents[0].text);

console.log('Operable criteria (keyboard, navigation, timing):');
operableCriteria.forEach(c => {
  console.log(`- ${c.id}: ${c.title} (Level ${c.level})`);
});

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Integration with Tools

WCAG criteria resources complement analysis tools:
1

Run analysis

Use analyze-with-axe, analyze-with-lighthouse, or analyze-mixed to find issues
const analysis = await analyzeWithAxe('https://example.com');
2

Look up criteria

For each issue, use the WCAG criterion ID to get full context
const criterion = await client.readResource({
  uri: `wcag://criteria/${issue.wcagCriterion}`
});
3

Apply remediation

Use suggestedActions from the criterion to guide fixes
const data = JSON.parse(criterion.contents[0].text);
console.log('Suggested actions:');
data.suggestedActions.forEach(action => console.log(`- ${action}`));

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Affected User Groups

The affectedUsers field uses these standardized values:
User GroupDescription
screen-readerUsers who rely on screen readers (blind, low-vision)
low-visionUsers with partial sight who may use magnification
color-blindUsers with color vision deficiencies
motor-impairmentUsers with limited mobility or dexterity
keyboard-onlyUsers who navigate without a mouse
cognitiveUsers with cognitive or learning disabilities
deafUsers who are deaf or hard of hearing
seizureUsers sensitive to flashing or motion

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Error Responses

Invalid criterion IDs return an error object: 
{
  "error": "Criterio WCAG 9.9.9 no encontrado"
}
Invalid level values: 
{
  "error": "Nivel inválido: B. Use A, AA o AAA"
}
Invalid principles: 
{
  "error": "Principio inválido: accessible. Use perceivable, operable, understandable o robust"
}

Contrast Thresholds

Specific contrast ratio requirements for criteria 1.4.3 and 1.4.6

Lighthouse Audits

Map Lighthouse audits to WCAG criteria

Analysis Tools

Tools that detect WCAG violations

Prompts

Use explain-wcag-criterion for detailed explanations

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Standards Reference

This resource is based on:
  • WCAG 2.1 (W3C Recommendation, June 2018)
  • Level A: 30 criteria
  • Level AA: 20 additional criteria (50 total)
  • Level AAA: 28 additional criteria (78 total)
For the official specification, see: WCAG 2.1 Guidelines

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